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Monarch butterflies’ ancestors migrated

The insects originated in North America, genetics study finds

A HISTORY OF TRAVEL Some monarch butterflies live in the tropics and stay put, but their ancestors were migratory North Americans, like these wintering in Mexico.

Sonia Altizer

The earliest monarch butterflies arose in North America and were migratory, contrary to what scientists believed. Over time, the butterflies evolved populations in other locations, some of which stay put year-round, scientists conclude October 1 in Nature.

Because many of the monarch’s closest butterfly relatives live in the tropics and do not migrate, “the thought was that the butterflies [came] from South and Central America and became migratory from resident populations,” says Tyler Flockhart, a conservation biologist who concentrates on monarchs at the University of Guelph in Canada. “But that doesn’t seem to be the case.”

Monarchs, Danaus plexippus, are famous for their annual migration from the United States and Canada to Mexico and back. But nonmigratory populations of the same species live in the tropics of Central and

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